When an explosively formed charge is detonated, a liner is set into motion by the incidental pressure wave. The liner is deformed by turning inside out, that is to say it is transformed into a projectile (or slug) whose front part is formed by the axial zone of the liner and whose rear part is a skirt formed by the periphery of the liner.
Patent FR2627580 describes such a charge.
When designing such a charge, the problem usually arises of how to make the liner integral with the charge casing.
Generally a solution is found whereby the liner is held in position axially by being shrunk fit onto the internal cylindrical surface of the casing.
Axial retention can also be ensured by means of an abutment formed by a rim, integral with the casing, and positioned in front of a peripheral circular zone of the liner.
Such known solutions are described in patent FR2657156.
However, they are not entirely satisfactory, in particular in the event that the liner material is a ductile material or a material for which the formation of the slug is perturbed by the presence of local stresses on the liner.
Thus, shrink-fitting generates stresses on the periphery of the liner which perturbs the formation and reproducibility of the slug skirt.
The presence of an abutment in front of a circular zone of the liner presents the risk of tearing off the skirt from the slug, thus seriously perturbing its stability.
Moreover, explosively-formed charges are subject, during storage phases, to thermal constraints which cause dilations whose magnitude differs for the explosive charge and the metal casing.
Such dilations (which generate constraints at the contact points) further complicate the design of the means to link the liner and the casing.
So as to increase the ballistic performances of the slugs, the thickness of the peripheral part of the liner in contact with the casing also has to be reduced.
When this part becomes too thin, gases generated by the detonation of the load can leak at the contact zone between the casing and liner, a zone which is already greatly stressed by the expansion of the products of the detonation.
These leaks seriously perturb the formation of the slug skirt thereby reducing its ballistic performances.